Compressor governor



Nov. 16, 1937.

B. s. AIKMAN 2,099,416

, COMPRES SOR GOVERNOR /Vo/7 00/2 dacf/oy mafer/a( 2 Sheets-Sheet 2 Filed May 15, 1956 mm-ml llli 1" [In qllll INVENTOR BURTON SAIKMAN ATTORNEY Patented Nov. 16, 1937 PATENT OFFICE COMPRESSOR GOVERNOR Burton S. Aikman, Wilkinsburg, The Westinghouse Air Brake merding,

Pa., assignor to Company, Wil- 'Pa., a corporation of Pennsylvania Application May 15, 1936, Serial No. 79,937

18 Claims.

This invention relates to switches of the type adapted to be operated in response to variations in the pressure of the fluid supplied thereto.

It is an object of this invention to provide. a

5 switch of this type which is operative in response to relatively small variations in the pressure of the fluid supplied thereto.

A further object of the invention is to provide a switch of this type, which incorporates means to adjustably vary the pressure to which it is adapted to respond to interrupt or to complete the v circuit controlled thereby.

Another object of this invention is to provide a switch of this type and in which the force 1 operative to maintain the switch contacts in engagement is not aifected by changes in the adjustment of the switch.

A further object of this invention is to provide an improved fluid pressure switch.

Other objects of the invention and features of novelty will be apparent from the following description taken in connection with the accompanying drawings in which,

Fig. 1 is a view, largely in section, of a switch 5 provided by my invention,

Fig. 2 is a view similar to Fig. 1, but showing the parts of the switch in a different operating relationship than they are shown in Fig. 1,

Fig. 3 is a view similar to Figs. 1 and 2, but

30 showing the parts of the switch in a still diiferent operating relationship, and

Fig. 4 is a sectional view taken substantially along the line 4-4 of Fig. 3.

Referring to the drawings, the switch therein illustrated comprises a body or frame indicated generally by the reference numeral I. This body is preferably formed of magnetic material, such.

as cast iron, and has formed integral therewith a hollow, substantially tubular core portion 3 on which is mounted a winding 4.

The body or frame I has formed thereon spaced arms 6, as is best shown in Fig. 4 of the drawings, which carry a pin 8 on which is mounted a switch lever I which may be formed of any suitable material, and which has adjacent the end thereof an armature portion I2 formed of magnetic material. The armature portion I2 is adapted to be attracted to the end of the core 3 by the flux field created in the region of the end of the core on energization of the winding 4.

The switch lever I I) has secured thereto, but insulated therefrom, a contact I 4 having a substantially spherical end portion I 5 carried by a resilient arm which is yieldingly pressed against .aface of the lever I 0 by means of a spring I6,

The spherical end portion I5 of the contact I4 is adapted at certain times, as will hereinafter more fully appear, to engage a stationary contact I8 which is secured to, but insulated from, a portion of the body or frame I. The stationary contact I8 is connected by way of a wire with one terminal of a source of electric current.

The contact I4 carried by the switch lever I 0 is connected by way of a wire 22 with a terminal post 24 mounted on, but insulated from, the body or frame I. The terminal post 24 is connected by way of a wire 26 with one terminal of the apparatus to be controlled, which may be the driving motor for a fluid compressor. The other terminal of this motor or other apparatus is connected to the other terminal of the source of electric current, that is, to the terminal other than the oneto which the wire 20 is connected.

The switch lever II] has associated therewith a torsional spring 28, one end 30 of which extends through an opening 32 through the switch lever I0 while the other end 34 extends through an opening in one of the arms 6 of the body or frame I, as is best shown in Fig. 4 of the drawings. The spring 28. operates to yieldingly urge the switch lever ID in a counterclockwise direction, as viewed in the drawings, so as to move the armature I2 away from the end of the core 3, and to move the spherical end portion I5 of the contact I4 away from the stationary contact I8.

The switch provided by this invention includes means for controlling movement of the switch lever I0. As shown in the drawings this means comprises a latch lever 36 which has one end thereof rigidly secured to the body or frame I. The latch lever 36 has a shoulder 38 formed thereon, and'adapted to be engaged by a projection 40 on the lower end of the switch lever ID to limit movement of the switch lever I 0 in a counterclockwise direction by the spring 28.

The latch lever 36 is formed of resilient material and is arranged on the body or frame I so that the free end of the lever is urged upwardly with considerable force. When the projection 40 on the switch lever II! is in engagement with the shoulder 38, the lower end of the projection 40 is engaged by the face of the latch lever 36 and prevents further upward-movement of the free end of the lever 36.

Thelatch lever 36 has, in addition, a shoulderindicated at 42 formed thereon, and which at certain times, as will hereinafter-more fully appear, is adapted to be engaged by the projection 40 on the switch lever II] to limit movement of the sw tc lever in by t e spr The switch provided by this-invention also includes means for controlling the supply of current to the winding l and for controlling operation 52 which is mounted on the end of a resilient portion of the contact 55. The spherical end portion 52 is adapted to engage the stationary contact I8.

The contact is connected by way of a wire with one terminal of the winding l, while the other terminal of the winding 5 is connected by way of a wire 55 to the terminal of the source of electric current opposite from the terminal to which the wire 20 is connected.

The lever 56 has a bore extending therethrough and a rod 6ll,-which is formed of a suitable nonconclucting materiaL, such as fiber or moulded plastic composition, is positioned in this bore.

The rod 60 is slidable in the bore in the lever 5'6 and is somewhat longer than this lever. The lower end of the rod 50 is engaged by an adjusting screw 52 which is adjustably secured in the end of the latch lever 56, while the upper end of the rod 50 is adapted to engage the contact 55. The adjusting screw is locked in the adjusted position by means of a lock nut 55.

The upper end of the lever 56 has secured thereto one end of a spring 55 and the other end of this spring secured in an eye in a threaded member '66 which is adjustably secured relative to the body or frame l by means of a knurled nut 58. The nut 68 is adjusted so as to subject the spring fi lto substantial tension, thereby urging the lever 56 to move in a clockwise direction about the pin 6 and moving the spherical end portion 52 of the contact 50 into engagement with the stationary contact l8.

The switch provided by this invention also includes means responsive to the pressure of the fluid in'a chamber for effecting movement of the lever 46. As shown in the drawings this means comprises a movable abutment in the form of a diaphragm 10, which has its periphery clamped between the body or frame land a cover 172. The diaphragm i0 is subject on one side to the pressure of the fluid in a chamber M which is connected by way of a passage and pipe 16 with the source of fluid under pressure to which the switch is intended to respond to interrupt or complete the circuit control ed thereby.

The diaphragm in is engaged on the other side by a plunger 18 which is slidable in a bore in the stem which terminates in a curved end portion which is engaged by one end of a push rod Bil which projects through an opening in the armature E2 of the switch lever ill, and which has its other end extending into a recess indicated at 82 in the face of the lever 55.

The cover 112 has stops 861 formed thereon which are adapted to be engaged by a face of the diaphragm M to limit movement of the diaphragm 10 to right, as viewed in the drawings, and thereby limit movement of the plunger Hi, the push spring M.

The switch is shown in Fig. 1 of the drawings in the position which'it assumes when the pressure of the fluid in the chamber Ml is below the value at which the switch is intended to respond to complete the circuit controlled thereby, with. lever ited by engagement of the projection MI with the shoulder '58 on the latch lever 36, while upward movement of the free end of the latch lever 35 is prevented by engagement of the upper face of the latch lever with the projection ll] on the switch lever llll.

The adjusting screw 62 carried by the free end of thelatch lever 36 is maintained away from the lower face of the lever 56, and the rod 50 may slide downwardly in the bore in the lever 55 away from the contact 50. At this time the lever 415 is urged in a clockwise direction by the spring 56 to the position in which its movement is. limited by the engagement of the diaphragm 115 with the If at this time the line switch, which controls I the supply of current to the switch provided by this invention is closed, a circuit will be established through the winding 5. This circuit will be by way of the wire fill which is connected to one terminal of the source of electric current, the stationary contact iii, the spherical end portion 52 and the contact 55, the wire 55 to one terminal of the winding t, and through this Winding to the wire 55 which is connected to the other terminal of the source of electric current. i

On the completion of the circuit through the winding 5 a strong flux field will be created in the .regiOn adjacent the end of the core 3 and the spring 28 with the result that the armature i2 is moved fromtheposition in which it is shown in Fig. 1 of the drawings into engagement with the end of the core 3, which is the position in which it is shown in Fig. 2 of the drawings.

On this movement of the switch lever ill, the projection 40 on the lower end of the switch lever moves away from the projection 55 on the latch lever 36 far enough that the face of the projection M is located to the left of the shoulder 42 on the latch lever 36.

When the projection Mlon the switch lever i5 is moved to this position the free end of the latch lever 35 is moved upwardlydue to the In herent resiliency of the material of which t latch lever is constructed.

On this movement of the free end of the latch lever 55, the adjusting screw 62 moves the rod 60 upwardly in the bore in the member lfi. Theforce exerted by the latch lever 36 upon the rod 65 exceeds the opposing force exerted on this rod by the contact 55, and the upper end of the rod 60 will engage the contact 55 and move it so that the spherical end portion 52 is moved away from the stationary contact I6, thereby interrupting the circuit through the winding 4.

The free end of the latch lever 36 will continue to move upwardly until the end of the adjusting screw 62 engages the lower face of the lever 46, while the shoulder 42 on the latch lever 36 will be moved into the path of movement of the projection 40 on the switch lever I 50 as to prevent movement of switch lever ID by the torsional spring 28 when the circuit through the winding 4 is interrupted.

When the switch lever III is moved. from the position in which it is shown in Fig. 1 of the drawings by the magnetic flux produced adjacent the core 3 to the position in which it is shown in Fig. 2 of the drawings, the spherical end portion IS on the contact I4 is pressed into engagement to the stationary contact I8 and is firmly held in engagement therewith by the inherent resiliency of the material of which the contact [4 is constructed and by the spring l6.

On movement of the spherical end portion l5 of the contact l4 into engagement with the stationary contact l8 a circuit is established through the motor or other apparatus which is controlled by this switch. This circuit includes the wire 20, which is connected to one terminal of the source of electric current, the stationary contact 18, the contact E4, the wire 22 to the terminal post 24 and thence by way of the wire 26 to one terminal of the motor. The other terminal of the motor is connected to the other terminal of the source of electric current.

The switch is now substantially in the position in which it is shown in Fig. 2 of the drawings. In this position the spherical end portion 52 of the contact'Sll is out of engagement with the stationary contact 18, being held away from this contact by the rod 60 which is forced upwardly by the latch lever 36.

In addition, in this position of the. switch, the switch lever 18 is in the position in which the spherical end portion l5 of the contact I4 is in engagement with the stationary contact l6 so as to complete the circuit to the motor or other apparatus to be controlled, while movement of the switch lever ill by the torsional spring 28 is prevented by engagement of the projection 40 with the shoulder 42 on the latch lever 36.

At this time the adjusting screw 62 engages the lower face of the lever 46 and exerts a force on this lever supplementing that of spring 64 and tending to move the lever 46 in a clockwise direction about the pin 8.

On the supply of electric current to the motor or other apparatus controlled by the switch, the compressor or device driven by this motor or other apparatus is operated to supply fluid under pressure to the reservoir to which the pipe 16 is connected, and as the pressure in this reservoir builds up there will be an increase in the pressure of the fluid in the chamber 14 on the face of the diaphragm 10.

On an increase in the pressure of the fluid in the chamber 14 there will be an increase in the force exerted on the diaphragm l0, and this force will be transmitted through the plunger 18 and the push rod 80 to the lever 46 and will tend to move this lever against the opposing force of the spring 64 and the latch lever 36.

As the pressure of the fluid in the chamber I4 builds up the diaphragm 18 will be moved to the left, as viewed in the drawings, and this movement will be transmitted to the lever 46 to move this lever in a counterclockwise direction. On

this movement of the lever 46, the lower end of the lever 46 will press against the adjusting screw 62 and move the free end of the latch lever 36 downwardly so that the shoulder 42 is moved away from the projection 40.

When the pressure of the fluid in the chamber 14 has increased to a predetermined relatively high value the movement of .the diaphragm 18 will be sufficient to move the lever 46 far enough .to move the latch lever 36 downwardly so that the shoulder 42 is moved out of the path of movement of the projection 48 on the switch lever Hi.

When the shoulder 42 is moved out of the path of movement of the projection 48 the switch lever i0 is no longer held by the shoulder 42 and the torsional spring 28 will move the switch lever H1 in a counterclockwise direction about the pin 8, thereby moving the spherical end portion I5 of the contact 14 away from the stationary contact l8, thus interrupting the circuit to the motor or other apparatus controlled by the switch. The switch lever ID will be moved by the torsional spring 28 until the projection 40 thereon engages the shoulder 38 on the latch lever 36. The switch 4 the diaphragm 10, the spherical end portion 52 of the contact 50 is moved away from the stationary contact 18 so that it is no longer able to engage the stationary contact, as is clearly shown in Fig. 3 of the drawings.

As the circuit to the motor or other apparatus controlled by this switch is interrupted, the device driven thereby will not operate to supply fluid under pressure to the reservoir from which fluid is supplied by way of the pipe 16 to the chamber M. There will, therefore, be no further increase in the pressure of the fluid in the chamber 14.

On a subsequent reduction in the pressure of the fluid in the reservoir into which fluid is compressed by the device controlled by this switch, there will be a similar reduction in the pressure of the fluid in the chamber 14 on the face of the diaphragm 10, and a corresponding reduction in the force exerted by this fluid through the diaphragm 10, the plunger I8, and push rod 80 upon the lever 46 in opposition to the spring 64.

As a result of the reduction in the force exerted by the fluid under pressure in the chamber 14, the lever 46 will be moved in a clockwise direction by the spring 64, thereby moving the lower end of the lever 46 away from the adjusting screw 62. At this time the free end of the latch lever '36, which carries the adjusting screw 62, is prevented from moving upwardly by engagement of the upmr face of the latch lever with the projection 40 on the switch lever l0.

As the free end of the latch lever 36 is prevented from moving upwardly at this time, the

adjusting screw 62 will be spaced from the lower V As the lever 46 continues to move clockwise direction about the pin d the distance between. the lower end of the lever it and the adjusting screw 62 will increase and the rod til will be moved further downwardly in the bore in the lever it, while the contact till will move towards the free end of the lever M.

When the pressure of the fluid in the chamber i i falls to a relatively low value the lever it will be moved by the spring til substantially to the position in which the lever is shown in Fig. 1 of the drawings. However, before the lever it will be moved to this position, the pressure of the fluid in the chamber i l must fall to a somewhat lower value than was required to effect movement of a lever ll; awa r from the position in which it is shown in Fig. 1 of the drawings, as movement of the lever it away from this .position is opposed by the spring tit and by the latch lever 36, while movement of the lever it: towards the position in which it is, shown in Fig. l of the.

drawings is effected solely by the spring M without the aid of the latch lever it.

When the lever tit has moved substantially to On this movement of the. switch lever ill the projection lil is moved away from the shoulder 38 and isrnoved to a position to permit the free end of the latch lever it to move upwardly so that the shoulder it? is now in the path of movement of the projection it.

On upward movement of the free end of the latch lever lit the adjusting screw 62 presses against the lower end of the rod 60 and moves it upwardly in the bore in the lever it so that the upper end of the rod 6% engages the contact iii] and moves the spherical end portion 52 of the contact G away from the stationary contact it, thereby interrupting the circuit through the winding i.

The free end of the latch lever it continues to move upwardly until the adjusting screw t2 engages the lower end of the lever it. The adjusting screw M will thereafter press against the lever All; and exert a force on this lever supplementing the spring M and opposing movement of the lever M by the fluid under pressure in the chamber M.

On the interruption in the supply of current to the winding i the flux field adjacent the end of the core 3 diminishes, but the spring 28 is unable to move the switch lever it away from the core 3 as the projection til engages the shoulder it on the latch lever 36.

In this position of the switch lever ill the spherical end portion it of the contact it engages the stationary contact it to complete a circuit to the motor or other apparatus controlled by the switch and the device driven thereby is operated to compress fluid into the reservoir with which the pipe 76 communicates.

On an increase in the pressure of the fluid in this reservoir there will be a similar increase inthe pressure of the fluid in the chamber M! on the face of the diaphragm it and a correspond- .if. v aoeatie ing increase in the force exerted through the plunger it and the push rod 80 on the lever fit.

At this time movement of the lever it is opposed by the spring 64 and also by the latch lever 36 acting through theadjusting screw 62 which engages the lower end of the lever Mi. As a result the lever 46 will not be moved until there has been a substantial increase in the pressure of the fluid in the chamber M, and thereafter on a further increase in the pressure of the fluid in the chamber it, the lever lii will be moved in a counterclockwise direction and will move the free end of the latch lever 36 downwardly until the shoulder 412 is moved out of the path of movement of the projection in on the switch lever it! so as to permit the switch lever 00 to be moved to the open position by the torsional spring adjustably varied. This means comprises the knurled nut '68 which operates through. the threaded member 66 to control the tension on the spring fi l.

If the nut 68 is turned in one direction the tension on the spring t l -is increased, thereby increasing the force exerted by this spring on the lever it and producing' a corresponding increase in the value to which the pressure of the fluid in the chamber M must fall before the lever :15 will be moved. to the position to complete the circuit through the winding t and thereby complete the circuit controlled by this switch. In addition,there will be a similar increase in the pressure to which the fluid in the chamber it must increase before the lever it will be moved to a position to release the latch lever 36 and permit the switch lever 00 to be moved by the torsional spring 28 to move the spherical portion l5 of the contact Mi out of engagement with the stationary contact it and thereby interrupt the circuit to the motor or other apparatus controlled by the switch.

If the knurled nut se is turned in'the other j direction the tension on the spring 64 is decreased, thereby decreasing the force exerted by this spring on the lever M and producing a corresponding decrease in the value to which the.

pressure of the fluid in the chamber it must fall before the lever 46 .will be moved to the position I by this switch.

The switch provided by this invention also incorporates means by which the difierence in the pressures at which it operates to interruptthe circuit controlled thereby and the pressure at which it operates to complete the circuit may be adjustably varied. This means comprises the adjusting screw 62 which is carried by the latch lever 36. If this screw is turned in one direction the distance the free end of the latch lever may move before the, end of the adjusting screw 52 engages the lower end of the lever 46 will be re duced, and hence the portion of the shoulder 42 on the latch lever 38 which extends into the path of movement of the projection 40 on the switch lever ill will be reduced.

The distance which the free end of the latch lever 36 must be moved before the shoulder 42 is moved out of the'path of movement of the projection 40 to release the switch lever i and permit it to be moved by the torsional spring 28 to a position to interrupt ,the circuit controlled thereby will be correspondingly reduced, therefore, and there will be a similar reduction in the pressure to which the fluid underpressure in the chamber '14 on the face of the diaphragmlil must build up before ,the lever 46 will be moved 'far enough to move the free end of the latch lever this distance.

Similarly, if the adjusting screw 62 is turned ln'the opposite direction the distance which the free end of ,the latch lever 36 may move before the end of the adjusting screw 62 engages the lower end of the lever 46 will be increased and the portion of the shoulder 42 on the latch lever 36 which extends into the path of the projection 46 on ,the switch lever ill will be correspondingly increased. Likewise the distance which the free end of the latch lever 36 must be moved before the shoulder 42 is moved out of the path of movement of the projection 40 to release the switch lever ill and permit it to be moved by the torsional spring 28 to a position to interrupt the circuit controlled thereby will be increased, and there must be a similar increase in the pressure or the fluid in the chamber 14 before the lever 46 will be moved this distance.

It will be seen, however, that changes in the adjustment of either of. the adjusting means incorporated in this switch do not ail'ect in any way the pressure with which the spherical end portion ii on the contact I! is pressed into engagement with the stationary contact i8. This pressure remains the same and is determined by the inherent resiliency of the material of which the contact I4 is constructed, together with the force exerted by the spring i 6, and these are pr p tioned so as to insure that the spherical end p0 tlon l5 of the contact I 4 will firmly engage the stationary contact l8 to make good electrical connection with this contact.

It will be seen also that movement of the switch lever I 0 between. its switch open and switch closed positions occurs very rapidly so as to reduce arcing between the movable and stationary contacts and thereby reduce to a minimum the damage which occurs to these contacts.

While one embodiment of the improved switch provided by this invention has been illustrated and described in detail, it should be understood that the invention is not limited to these details of construction, and that numerous changes and modifications may be made without departing from the scope of the following claims.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In a switch device, in combination, a switch movable between an open position and a closed position, yielding means urging the switch to one of said positions, electro-responsive means for moving the switch against the yielding means, latch means for preventing movement or the switch by the yielding means, biasing means, said switch device having a chamber adapted to contain fluid under pressure, and means subject to the opposing pressures of the fluid in said chamber and of said biasing means for controlling said latch means and for also controlling the supply of current to the electro-responsive means.

2. In a switch device, in combination, a switch movable between an open position and a closed position, yielding means urging the switch to ne of said positions, electro-responsive means for moving the switch against the yielding means, latch means movable between a release position and a latching position, the latch means bein operative in the release position to permit movement of the switch between its positions by .the yielding means and in the latching position to prevent movement of the switch by the yielding means, biasing means, said switch device having a chamberadapted ,to contain fluid under. pressure, and movable abutment means subject to the opposing pressures of the biasing means and of the fluid in said chamber for moving the latch means from the latching position to the release position.

3. In a switch device, in combination, a switch movable between an open position and a closed position, yielding means urging the switch to one of its positions, eiectro-responsive means for moving the switch against the yielding means, latch means movable between a release position and. a latching position, the latch means being operative in the release position to permit movement of the switch between its positions by the yielding means and in the'latching position to prevent movement of the switch by the yielding means, biasing means, said switch device having a chamber adapted to contain fluid underpressure, and movable abutment means subject to the opposing pressures of ,the biasing means and of the fluid in said chamber for moving the latch means from the latching position to the release position and for controlling the supply of current to the electro-responsive means.

4. In a switch device, in combination, a switch movable between an open position and a closed position, yielding means urging the switch to one of its positions, electro-responsive means for moving the switch against the yielding means, latch means movable between a release position and a latching position, the latch means being operative in the release position to permit movement of the switch between its positions by the yielding means and in the latching position to pre-' vent movement of the switch by the yielding means, a member movable between spaced positions and controlling the latch means and the supply of current to the electro-responsive means, biasing means urging said member to one of said positions, said switch device having a chamber adapted to contain fluid under pressure, and a movable abutment subject to and operated on an increase of the pressure 01' the fluid in said chamber for moving the member to other of said posi-' tions.

5. In a switch device, in combination, a switch movable between an open position and a closed position, yielding means urging the switch to one of its positions, electro-responsive means for moving the switch against the yielding means, latch means movable between a release position and a latching position, the latch means being operative in the release position to permit movement of the switch between its positions by the yielding means and in the latching position to prevent movement of the switch by the yielding means, a member movable between the spaced positions, said member controlling the latch means and being operative on movement to one of its positions to move the latch means to the release position and on movement to the other of its positions to permit the latch means to move to the latching position, biasing means urging said member to one of said spaced positions, said switch device having a chamber adapted to con tain fluid under pressure, and movable abutment means subject to and operated on an increase in the pressure of the fluid in said chamber for moving the member to the other of the said spaced positions.

6. In a switch device, in combination, a switch movable between an open position and a closed position, biasing means associated with the switch and urging the switch to one of said positions, electro-responsive means for moving the switch against the biasing means, latch means movable between a release position and a latching position and operative in the latching position to prevent movement of the switch from one of said positions, yielding resistance means, said switch device having a chamber adapted to contain fluid under pressure, a member subject to the opposing pressures of the fluid in said chamber and of said yielding resistance means for moving the latch'meansfrom one of its positions to the other of its positions, and means controlled by said member and by said latch means .for controlling the supply of current to the electro-responsive means.

'7. In a switch device, incombination, a switch movable between an open position and a closed position, biasing means associated with the switch and urging the switch to one of said positions, electro-responsive means for moving the switch against the biasing means, latch means movable between a release position and a latching position'and operative in the latching position to prevent movement of the switch from one of the said positions to the other of said positions, yielding resistance means, said switch device having a chamber adapted to contain fluid under pressure, and a member subject to the opposing pressures of the fluid in said chamber and of said yielding resistance means for moving the latch means from the latching position to the release position, the switch being operative to control movement of the latch means from the release position to the latching position. I

8. In a switch device, in combination, a switch movable between an open position and a closed position, biasing means associated with the switch and urging the switch to one of said positions, electro-responsive means for moving the switch against the biasing means, latch means movable between a release position and a latching position and operative in the latching position to pre vent movement of the switch from one of the said positions to the other of the said positions, yielding resistance means, said switch device having a chamber adapted to'contain fluid under pressure, a member subject to the opposing pressures of the fluid in said chamber and of said yielding resistance means for moving the latch means from the latching position to a release position,

the switch being operative to control movement of the latch means from the release position to the latching position, and means controlled by said member and by the latch means for controlling the supply of current to the electro-responsive means.

9. In combination, a switch movable between an open position and a closed position, biasing means associated with the switch and urging the switch to the open position, electro-responsive means operative on the supply of current thereto to move the switch against the biasing means to the closed position, latch means associated with the switch and operative on movement of the switch to the closed position to prevent movement of the switch from said position, and means controlled by the latch means for controlling the supply of current to the electroresponsive means.

10. In combination, a switch movable between an open position and a closed position, biasing means associated with the switch and urging the switch to the open position, electro-responsive means operative on the supply of current thereto to move the switch against the biasing means to the closed position, latch means associated with the switch and operative on movement of the switch to the closed position to move to a latching position to prevent movement of the switch from the closed position, and means operative on movement of the latch means to the latching position to interrupt the supply of current to the electro-responsive means.

11. In a switch device, in combination, a switch movable between an open position and a closed position, biasing means associated with the switch and urging the switch to the open position, electro-responsive means operative of the supply of current thereto for moving the switch to the closed position, yielding resistance means, said switch device having a chamber adapted to contain fluid under pressure, and a. member subject to the opposing pressures of the fluid in said chamber and of the yielding resistance means and controlling the supply of current to said electro-responsive means.

12. In a switch device, in combination, a switch movable between an open position and a closed position, yielding resistance means associated with the switch and urging the switch to the open position, electro-responsive means operative on the supply of current thereto for moving the switch to the closed position, yielding resistance means, said switch device having a chamber adapted to contain fluid under pressure, a member movable between spaced positions and controlling the supply of current to said electroresponsive means, said member being subject to the opposing pressures of the yielding resistance means and of the fluid in said chamber, and other yielding resistance means controlled by the switch for opposing movement of said movable member from one of its positions to the other of its positions.

13. In a switch device, in combination, a switch movable between an open position and a closed position, electro-responsive means operative on the supply of current thereto to move the switch to the closed position, latch means movable between a release position and a latching position and operative on movement to the latching position to prevent movement of the switch from the closed position, yielding resistance means, said switch device having a chamber adapted to contain fluid under pressure, a movable member subject to the opposing pressure of the yielding resistance means and of the fluid in said chamher for moving said latch means from the latching position to the release position, and biasing means operating through the latch means and opposing movement of the movable member to move the latch means from the latching position to the release position, the switch being operable on movement of the latch means to the release position to render the biasing means inoperative to exert force on said movable member.

14. In a switch device, in combination, a switch movable between an open position and a closed position, electro-responsive means for controlling movement of the switch, latch means movable between a release position and a latching position and operative in said latching position to permit movement of the switch from one of said positions to the other of said positions and to prevent movement of the switch in the other direction, yielding resistance means, said switch device having a chamber adapted to contain fluid under pressure, and means subject to the opposing pressures of the yielding resistance means and of the fluid in said chamber for controlling the supply of current to the electro-responsive means and for controlling operation of the latch means.

15. In a switch device, in combination, a switch movable between an open position and a closed position, latch means movable between a release position-and a latching position and being operative in the latching position to permit movement of the switch from one of the said positions to the other of the said positions and to prevent movement of the switch in the other direction, yielding resistance means, said switch device having a chamber adapted to contain fluid under pressure, and means subject to the opposing pressures of the fluid in said chamber and of the yielding resistance means for controlling operation of the latch means.

16. In a switch device, in combination, a switch movable between an open position and a closed position, latch means movable between a release position and a latching position and being operative in the latching position to permit movement of the switch from one of the said positions to the other of the said positions and to prevent movement of the switch in the other direction, yielding resistance means, said switch device having a chamber adapted to contain fluid under tions to the other of the said positions and to prevent movement of the switch in the other direction, yielding resistance means, said switch device having a chamber adapted to contain fluid under pressure, means subject to the up posing pressures of the yielding resistance means and of the fluid in said chamber for moving the latch means from the latching position to the release position, and means associated with the switch and controlling movement of the latch means from the release position to the latching position.

18. In a switch device, in combination, a switch movable between an open position anda closed position, latch means movable between a release position and a latching position and being operative in the latching position to permit movement of the switch from one of the said positions to the other of the said positions and to prevent movement of the switch in the other direction, yielding resistance means, said switch device having a chamber adapted to contain fluid under pressure, a member subject'to the opt csing pressures of theyielding resistance means and of the fluid in said chamber for moving the latch means from its latching position to the release position, biasing means associated with the latch means and opposing movement of the latch means by said member, and means operative on movement of the switch to one of its positions to prevent saidbiasing means from exerting force on said member.

BURTON S. AIKMAN. 

